1. Field of the Invention
The present invention relates to an exhaust device for an outboard motor engine including an air pump arranged to feed air into an exhaust passage. The present invention also relates to an outboard motor including this exhaust device.
2. Description of Related Art
An exhaust device for a marine vessel engine according to a prior art is disclosed in U.S. Pat. No. 5,425,232. This exhaust device is provided in an engine installed inside a hull. The engine is a multi-cylinder engine. The engine is installed on a bottom of the hull such that a crankshaft extends along the front-rear direction of the hull. The engine drives a drive unit attached to the outside of a transom board.
The exhaust device is arranged to exhaust an exhaust gas of the engine into water from a propeller of the drive unit. In an inboard portion from the engine to the transom board of an exhaust passage of this exhaust device, a catalytic converter (hereinafter, simply referred to as “catalyst”) is provided.
This exhaust device includes an air pump arranged to supply secondary air into the exhaust passage from a position on the upstream side of the catalyst. “Secondary air” is air which has not passed through the inside of the engine. The air pump is attached to a lower portion of the engine. In addition, the air pump is driven by the engine according to rotation of the crankshaft transmitted via a transmission belt.